Musical Instrument Digital Interface (MIDI) is a format used in the creation, communication and/or playback of audio sounds, such as music, speech, tones, alerts, and the like. A device that supports the MIDI format playback may store sets of audio information that can be used to create various “voices.” Each voice may correspond to one or more sounds, such as a musical note by a particular instrument. For example, a first voice may correspond to a middle C as played by a piano, a second voice may correspond to a middle C as played by a trombone, a third voice may correspond to a D# as played by a trombone, and so on. In order to replicate the musical note as played by a particular instrument, a MIDI compliant device may include a set of information for voices that specify various audio characteristics, such as the behavior of a low-frequency oscillator, effects such as vibrato, and a number of other audio characteristics that can affect the perception of sound. Almost any sound can be defined, conveyed in a MIDI file, and reproduced by a device that supports the MIDI format.
A device that supports the MIDI format may produce a musical note (or other sound) when an event occurs that indicates that the device should start producing the note. Similarly, the device stops producing the musical note when an event occurs that indicates that the device should stop producing the note. An entire musical composition may be coded in accordance with the MIDI format by specifying events that indicate when certain voices should start and stop. In this way, the musical composition may be stored and transmitted in a compact file format according to the MIDI format.
MIDI is supported in a wide variety of devices. For example, wireless communication devices, such as radiotelephones, may support MIDI files for downloadable sounds such as ringtones or other audio output. Digital music players, such as the “iPod” devices sold by Apple Computer, Inc and the “Zune” devices sold by Microsoft Corporation may also support MIDI file formats. Other devices that support the MIDI format may include various music synthesizers, wireless mobile devices, direct two-way communication devices (sometimes called walkie-talkies), network telephones, personal computers, desktop and laptop computers, workstations, satellite radio devices, intercom devices, radio broadcasting devices, hand-held gaming devices, circuit boards installed in devices, information kiosks, various computerized toys for children, on-board computers used in automobiles, watercraft and aircraft, and a wide variety of other devices.